Re: [PATCH v3 09/14] xen/riscv: introduce decode_cause() stuff

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Fri, 2023-02-10 at 12:00 +1000, Alistair Francis wrote:
> On Wed, Feb 8, 2023 at 12:48 AM Oleksii Kurochko
> <oleksii.kurochko@xxxxxxxxx> wrote:
> > 
> > The patch introduces stuff needed to decode a reason of an
> > exception.
> > 
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> > ---
> > Changes in V3:
> >   - Nothing changed
> > ---
> > Changes in V2:
> >   - Make decode_trap_cause() more optimization friendly.
> >   - Merge the pathc which introduces do_unexpected_trap() to the
> > current one.
> > ---
> >  xen/arch/riscv/traps.c | 85
> > +++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 84 insertions(+), 1 deletion(-)
> > 
> > diff --git a/xen/arch/riscv/traps.c b/xen/arch/riscv/traps.c
> > index ccd3593f5a..f2a1e1ffcf 100644
> > --- a/xen/arch/riscv/traps.c
> > +++ b/xen/arch/riscv/traps.c
> > @@ -4,10 +4,93 @@
> >   *
> >   * RISC-V Trap handlers
> >   */
> > +#include <asm/csr.h>
> > +#include <asm/early_printk.h>
> >  #include <asm/processor.h>
> >  #include <asm/traps.h>
> > +#include <xen/errno.h>
> > +#include <xen/lib.h>
> > 
> > -void do_trap(struct cpu_user_regs *cpu_regs)
> > +static const char *decode_trap_cause(unsigned long cause)
> > +{
> > +    static const char *const trap_causes[] = {
> > +        [CAUSE_MISALIGNED_FETCH] = "Instruction Address
> > Misaligned",
> > +        [CAUSE_FETCH_ACCESS] = "Instruction Access Fault",
> > +        [CAUSE_ILLEGAL_INSTRUCTION] = "Illegal Instruction",
> > +        [CAUSE_BREAKPOINT] = "Breakpoint",
> > +        [CAUSE_MISALIGNED_LOAD] = "Load Address Misaligned",
> > +        [CAUSE_LOAD_ACCESS] = "Load Access Fault",
> > +        [CAUSE_MISALIGNED_STORE] = "Store/AMO Address Misaligned",
> > +        [CAUSE_STORE_ACCESS] = "Store/AMO Access Fault",
> > +        [CAUSE_USER_ECALL] = "Environment Call from U-Mode",
> > +        [CAUSE_SUPERVISOR_ECALL] = "Environment Call from S-Mode",
> > +        [CAUSE_MACHINE_ECALL] = "Environment Call from M-Mode",
> > +        [CAUSE_FETCH_PAGE_FAULT] = "Instruction Page Fault",
> > +        [CAUSE_LOAD_PAGE_FAULT] = "Load Page Fault",
> > +        [CAUSE_STORE_PAGE_FAULT] = "Store/AMO Page Fault",
> > +        [CAUSE_FETCH_GUEST_PAGE_FAULT] = "Instruction Guest Page
> > Fault",
> > +        [CAUSE_LOAD_GUEST_PAGE_FAULT] = "Load Guest Page Fault",
> > +        [CAUSE_VIRTUAL_INST_FAULT] = "Virtualized Instruction
> > Fault",
> > +        [CAUSE_STORE_GUEST_PAGE_FAULT] = "Guest Store/AMO Page
> > Fault",
> > +    };
> > +
> > +    if ( cause < ARRAY_SIZE(trap_causes) && trap_causes[cause] )
> > +        return trap_causes[cause];
> > +    return "UNKNOWN";
> > +}
> > +
> > +const char *decode_reserved_interrupt_cause(unsigned long
> > irq_cause)
> > +{
> > +    switch ( irq_cause )
> > +    {
> > +    case IRQ_M_SOFT:
> > +        return "M-mode Software Interrupt";
> > +    case IRQ_M_TIMER:
> > +        return "M-mode TIMER Interrupt";
> > +    case IRQ_M_EXT:
> > +        return "M-mode TIMER Interrupt";
> 
> Wrong string here
> 
> Alistair
Nice catch.
Thanks.
> 
> > +    default:
> > +        return "UNKNOWN IRQ type";
> > +    }
> > +}
> > +
> > +const char *decode_interrupt_cause(unsigned long cause)
> > +{
> > +    unsigned long irq_cause = cause & ~CAUSE_IRQ_FLAG;
> > +
> > +    switch ( irq_cause )
> > +    {
> > +    case IRQ_S_SOFT:
> > +        return "Supervisor Software Interrupt";
> > +    case IRQ_S_TIMER:
> > +        return "Supervisor Timer Interrupt";
> > +    case IRQ_S_EXT:
> > +        return "Supervisor External Interrupt";
> > +    default:
> > +        return decode_reserved_interrupt_cause(irq_cause);
> > +    }
> > +}
> > +
> > +const char *decode_cause(unsigned long cause)
> > +{
> > +    if ( cause & CAUSE_IRQ_FLAG )
> > +        return decode_interrupt_cause(cause);
> > +
> > +    return decode_trap_cause(cause);
> > +}
> > +
> > +static void do_unexpected_trap(const struct cpu_user_regs *regs)
> >  {
> > +    unsigned long cause = csr_read(CSR_SCAUSE);
> > +
> > +    early_printk("Unhandled exception: ");
> > +    early_printk(decode_cause(cause));
> > +    early_printk("\n");
> > +
> >      die();
> >  }
> > +
> > +void do_trap(struct cpu_user_regs *cpu_regs)
> > +{
> > +    do_unexpected_trap(cpu_regs);
> > +}
> > --
> > 2.39.0
> > 
> >